Electronic component, method of manufacturing the same, and mount structure of electronic component

ABSTRACT

An electronic component includes a main body, first and second external electrodes, and a water-repellent film. The first and second external electrodes are provided on a portion of a surface of the main body. The water-repellent film is provided on another portion of the surface of the main body and on a surface of the first external electrode. The water-repellent film contains a non-cross-linked silicone resin. An angle of contact of water of about 25° C. with the water-repellent film is not less than about 100° and not greater than about 160°.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic component, a method ofmanufacturing the same, and a mount structure of an electroniccomponent.

2. Description of the Related Art

Reduction in size and thickness has recently been accelerated inelectronic devices such as a portable telephone and a portable musicplayer. Concurrently, for example, reduction in size of an electroniccomponent contained in an electronic device has also been demanded. Suchelectronic devices are used in various environments, and improvements inthe reliability of electronic components in various environments havebeen desired.

As described in International Publication WO2002/082480, ion migrationin an electronic component has recently given rise to a problem in somecases. Ion migration occurs, for example, as follows. A temperaturedifference between an electronic component and outside air causescondensation at a surface of the electronic component, and waterdroplets produced due to condensation form at the surface of theelectronic component, a water film which connects external electrodes toeach other. When a voltage is applied across the external electrodes ofthe electronic component in such a state, ionized metallic species isdissolved and precipitated from the external electrodes in the waterfilm. This problem occurs more noticeably when the electronic componentis mounted on a car placed in a severe environment. WO2002/082480describes providing a water-repellent film between external electrodesin order to suppress the occurrence of ion migration. WO2002/082480describes formation of a water-repellent film with the use of across-linked silane coupling agent which contains fluorine.

In general, an electronic component is used as being mounted on a mountsubstrate with the use of solder. However, an electronic componentprovided with a water-repellent film may have low mount ability.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide an electroniccomponent with excellent mountability with the use of solder while theoccurrence of ion migration is significantly reduced or prevented, amethod of manufacturing the same, and amount structure of an electroniccomponent.

An electronic component according to a preferred embodiment of thepresent invention includes an electronic component main body, first andsecond external electrodes, and a water-repellent film. The first andsecond external electrodes are provided on a portion of a surface of theelectronic component main body. The water-repellent film is provided onanother portion of the surface of the electronic component main body anda surface of the first external electrode. The water-repellent filmcontains a non-cross-linked silicone resin. An angle of contact of waterof about 25° C. with the water-repellent film preferably is not lessthan about 100° and not greater than about 160°, for example.

An electronic component according to another preferred embodiment of thepresent invention includes an electronic component main body, first andsecond external electrodes, and a water-repellent film. The first andsecond external electrodes are provided on a portion of a surface of theelectronic component main body. The water-repellent film is provided onanother portion of the surface of the electronic component main body anda surface of the first external electrode. The water-repellent filmcontains a non-cross-linked silicone resin. The non-cross-linkedsilicone resin preferably has a weight-average molecular weight not lessthan about 7400 g/mol and not greater than about 8000 g/mol, forexample.

An electronic component according to another preferred embodiment of thepresent invention includes an electronic component main body, first andsecond external electrodes, and a water-repellent film. The first andsecond external electrodes are provided on a portion of a surface of theelectronic component main body. The water-repellent film is provided onanother portion of the surface of the electronic component main body anda surface of the first external electrode. The water-repellent film issoluble in an organic solvent.

An electronic component according to another preferred embodiment of thepresent invention includes an electronic component main body, first andsecond external electrodes, and a water-repellent film. The first andsecond external electrodes are provided on a portion of a surface of theelectronic component main body. The water-repellent film is provided onanother portion of the surface of the electronic component main body anda surface of the first external electrode. The water-repellent film issoluble in a solvent contained in a solder flux.

An electronic component according to another preferred embodiment of thepresent invention includes an electronic component main body, first andsecond external electrodes, and a water-repellent film. The first andsecond external electrodes are provided on a portion of a surface of theelectronic component main body. The water-repellent film is provided onanother portion of the surface of the electronic component main body anda surface of the first external electrode. The water-repellent filmpreferably is a silicone resin film having a thickness not greater thanabout 200 nm, for example.

An outermost layer of each of the first and second external electrodespreferably contains at least one of Sn, Cu, and Ag.

The electronic component main body preferably includes first and secondmain surfaces extending along a length direction and a width direction,first and second side surfaces extending along the length direction anda thickness direction, and first and second end surfaces extending alongthe width direction and the thickness direction. On the second mainsurface, a tip end portion of the first external electrode and a tip endportion of the second external electrode are opposed to each other inthe length direction. The water-repellent film is located on a portionof the second main surface, which is located between the tip end portionof the first external electrode and the tip end portion of the secondexternal electrode.

The water-repellent film preferably extends across another portion ofthe surface of the electronic component main body and the surface of thefirst external electrode.

The water-repellent film preferably covers the entire surface of anexposed portion of the electronic component main body and each of thefirst and second external electrodes.

The solvent contained in the solder flux preferably is an organicsolvent.

The organic solvent preferably includes at least one selected from thegroup consisting of an ether-based organic solvent, an alcohol-basedorganic solvent, a hydrocarbon-based organic solvent, a ketone-basedsolvent, an ester-based solvent, and a glycol-ether-based solvent.

The solvent preferably has a solubility parameter (an SP value) of notless than about 7.0 and not greater than about 14.0, for example.

The water-repellent film preferably is a silicone resin film having athickness not greater than about 100 nm, for example.

The silicone resin film preferably contains a non-cross-linked siliconeresin.

A method of manufacturing an electronic component according to anotherpreferred embodiment of the present invention includes the steps offorming a first external electrode and a second external electrode on aportion of a surface of an electronic component main body and providingon another portion of the surface of the electronic component main bodyand a surface of the first external electrode, a water-repellent filmcontaining a non-cross-linked silicone resin, of which an angle ofcontact with water of about 25° C. is not less than about 100° and notgreater than about 160°, for example.

A method of manufacturing an electronic component according to anotherpreferred embodiment of the present invention includes the steps offorming a first external electrode and a second external electrode on aportion of a surface of an electronic component main body and providinga water-repellent film containing a non-cross-linked silicone resinhaving a weight-average molecular weight not less than about 7400 g/moland not more than about 8000 g/mol on another portion of the surface ofthe electronic component main body and a surface of the first externalelectrode, for example.

A method of manufacturing an electronic component according to anotherpreferred embodiment of the present invention includes the steps offorming a first external electrode and a second external electrode on aportion of a surface of an electronic component main body and providinga water-repellent film soluble in an organic solvent on another portionof the surface of the electronic component main body and a surface ofthe first external electrode.

A method of manufacturing an electronic component according to anotherpreferred embodiment of the present invention includes the steps offorming a first external electrode and a second external electrode on aportion of a surface of an electronic component main body and providinga water-repellent film soluble in a solvent contained in a solder fluxon another portion of the surface of the electronic component main bodyand a surface of the first external electrode.

In the step of providing a water-repellent film, the water-repellentfilm preferably is provided by immersing the electronic component mainbody having the first and second external electrodes formed in atreatment solution containing the non-cross-linked silicone resin,followed by drying.

A mount structure of an electronic component according to a preferredembodiment of the present invention includes the electronic componentdescribed above, amount substrate, and solder. The electronic componentis mounted on the mount substrate. The solder joins the electroniccomponent and the mount substrate to each other.

A water-repellent film preferably is not provided at a junction betweenthe electronic component and the mount substrate.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an appearance of an electroniccomponent according to a first preferred embodiment of the presentinvention.

FIG. 2 is a cross-sectional view of the electronic component in FIG. 1viewed in a direction of an arrow II-II.

FIG. 3 is a cross-sectional view of a mount structure of an electroniccomponent according to the first preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An electronic component, a method of manufacturing the same, and amountstructure of an electronic component according to various preferredembodiments of the present invention will be described hereinafter withreference to the drawings. In the description of the preferredembodiments below, the same or corresponding elements in the drawingshave the same reference characters allotted and description thereof willnot be repeated. A drawing referred to in a preferred embodiment isschematic. A scale of a dimension of an object drawn in the drawings maybe different from a scale of a dimension of an actual object. A scale ofa dimension of an object may be different between the drawings. Aspecific scale of a dimension of an object should be determined withreference to the description below.

First Preferred Embodiment

FIG. 1 is a perspective view showing an electronic component accordingto a first preferred embodiment of the present invention. FIG. 2 is across-sectional view of the electronic component in FIG. 1 viewed in adirection of an arrow II-II. FIG. 1 does not depict a water-repellentfilm 20.

As shown in FIGS. 1 and 2, an electronic component 1 includes anelectronic component main body 10 preferably having a parallelepiped orsubstantially parallelepiped shape. An electronic component main body 10includes first and second main surfaces 10 a and 10 b, first and secondside surfaces 10 c and 10 d, and first and second end surfaces 10 e and10 f. Each of the first and second main surfaces 10 a and 10 b extendsalong a length direction L and a width direction W. Each of the firstand second side surfaces 10 c and 10 d extends along a thicknessdirection T and a length direction L. Each of the first and second endsurfaces 10 e and 10 f extends along a thickness direction T and a widthdirection W. The length direction L, the width direction W, and thethickness direction T are orthogonal to one another.

In preferred embodiments of the present invention, a “parallelepiped”includes a parallelepiped of which corner portions or ridge lineportions are rounded. That is, a member in a “parallelepiped” shapeincludes a member including first and second main surfaces, first andsecond side surfaces, and first and second end surfaces in general.Projections and recesses may be provided in a portion or in the entiretyof the main surfaces, the side surfaces, and the end surfaces.

A dimension of the electronic component main body 10 is not particularlylimited. For example, a dimension of a thickness of the electroniccomponent main body 10 is preferably not less than about 0.1 mm and notgreater than about 3.0 mm, a dimension of a length of the electroniccomponent main body 10 is preferably not less than about 0.2 mm and notgreater than about 3.5 mm, and a dimension of a width of the electroniccomponent main body 10 is preferably not less than about 0.1 mm and notgreater than about 3.5 mm. The electronic component main body 10contains ceramics as appropriate in accordance with a function of theelectronic component 1. Specifically, when the electronic component 1functions as a capacitor, the electronic component main body 10preferably contains dielectric ceramics. Specific examples of dielectricceramics include BaTiO3, CaTiO₃, SrTiO₃, CaZrO₃, and other suitabledielectric ceramics. To the electronic component main body 10, forexample, a subcomponent such as an Mn compound, an Mg compound, an Sicompound, an Fe compound, a Cr compound, a Co compound, an Ni compound,a rare-earth compound, and other suitable subcomponents may be added asappropriate, in accordance with characteristics required of electroniccomponent 1.

When the electronic component 1 is a piezoelectric component, theelectronic component main body 10 preferably contains piezoelectricceramics. Piezoelectric ceramics are specifically exemplified by PZT(lead zirconate titanate)-based ceramics, for example.

When the electronic component 1 is, for example, a thermistor, theelectronic component main body 10 preferably contains semiconductorceramics. Semiconductor ceramics are specifically exemplified byspinel-type ceramics, for example.

When the electronic component 1 is, for example, an inductor, theelectronic component main body 10 preferably contains magnetic ceramics.Magnetic ceramics are specifically exemplified by ferrite ceramics, forexample.

As shown in FIG. 2, a plurality of first internal electrodes 11 and aplurality of second internal electrodes 12 are provided in theelectronic component main body 10. Each of the first internal electrodes11 preferably have a rectangular or substantially rectangular shape in aplan view. The first internal electrodes 11 are provided in parallel orsubstantially in parallel to each of the first and second main surfaces10 a and 10 b. That is, the first internal electrodes 11 are providedalong the length direction L and the width direction W. The firstinternal electrodes 11 are exposed at the first end surface 10 e and notexposed at the first and second main surfaces 10 a and 10 b, the firstand second side surfaces 10 c and 10 d, and the second end surface 10 f.

Each of the second internal electrodes 12 preferably has a rectangularor substantially rectangular shape in a plan view. The second internalelectrodes 12 are provided in parallel or substantially in parallel toeach of the first and second main surfaces 10 a and 10 b. That is, thesecond internal electrodes 12 are provided along the length direction Land the width direction W. The second internal electrodes 12 are exposedat the second end surface 10 f. The second internal electrodes 12 arenot exposed at the first and second main surfaces 10 a and 10 b, thefirst and second side surfaces 10 c and 10 d, and the first end surface10 e.

The first and second internal electrodes 11 and 12 are providedalternately along the thickness direction T. The first internalelectrodes 11 and the second internal electrodes 12 adjacent to eachother in the thickness direction T are opposed to each other with aceramic g interposed therebetween. The ceramic portion 10 g preferablyhas a thickness approximately not less than about 0.5 μm and not greaterthan about 10 μm, for example.

Each of the first and second internal electrodes 11 and 12 is composedof an appropriate conductive material. Each of the first and secondinternal electrodes 11 and 12 is preferably composed, for example, of ametal selected from the group consisting of Ni, Cu, Ag, Pd, and Au or analloy containing one or more metals selected from the group consistingof Ni, Cu, Ag, Pd, and Au (for example, an Ag—Pd alloy). Each of thefirst and second internal electrodes 11 and 12 preferably has athickness, for example, of approximately not less than about 0.3 μm andnot greater than about 2.0 μm.

The electronic component 1 further includes a first external electrode13 and a second external electrode 14. The first external electrode 13and the second external electrode 14 are provided on a portion of thesurface of electronic component main body 10. Specifically, the firstexternal electrode 13 extends across the entire surface of the first endsurface 10 e and a portion of the surface of each of the first andsecond main surfaces 10 a and 10 b and the first and second sidesurfaces 10 c and 10 d. The first external electrode 13 is electricallyconnected to the first internal electrode 11 at the first end surface 10e.

The second external electrode 14 extends across the entire surface ofthe second end surface 10 f and a portion of the surface of each of thefirst and second main surfaces 10 a and 10 b and first and the secondside surfaces 10 c and 10 d. The second external electrode 14 iselectrically connected to the second internal electrode 12 at the secondend surface 10 f.

In each of the first and second main surfaces 10 a and 10 b and thefirst and second side surfaces 10 c and 10 d, a tip end portion of thefirst external electrode 13 in the length direction L and a tip endportion of the second external electrode 14 in the length direction Lare opposed to each other in the length direction L.

An outermost layer of the first external electrode 13 preferablycontains at least one of Sn, Cu, and Ag, for example. Specifically, thefirst external electrode 13 includes a first electrode layer 13 a, asecond electrode layer 13 b, and a third electrode layer 13 c.

The first electrode layer 13 a is provided on a portion of the surfaceof the electronic component main body 10. The first electrode layer 13 ais defined by a fired electrode layer. The fired electrode layer refersto an electrode layer obtained by firing a paste layer obtained byapplying a paste containing conductive particles. The conductiveparticles contained in the fired electrode layer may preferably be, forexample, particles containing at least one of Cu, Ni, Ag, Pd, an Ag—Pdalloy, and Au.

The second electrode layer 13 b is provided on a surface of the firstelectrode layer 13 a. The second electrode layer 13 b may preferably bedefined by a plated layer. In the present preferred embodiment, thesecond electrode layer 13 b is preferably defined by a Ni plated layer.

The third electrode layer 13 c is provided on a surface of the secondelectrode layer 13 b. The third electrode layer 13 c may preferably bedefined by a plated layer. In the present preferred embodiment, thethird electrode layer 13 c preferably is defined by a Sn plated layer.

An outermost layer of the second external electrode 14 preferablycontains at least one of Sn, Cu, and Ag. Specifically, the secondexternal electrode 14 includes a first electrode layer 14 a, a secondelectrode layer 14 b, and a third electrode layer 14 c.

The first electrode layer 14 a is provided on a portion of the surfaceof the electronic component main body 10. The first electrode layer 14 ais preferably defined by a fired electrode layer. The fired electrodelayer refers to an electrode layer obtained by firing a paste layerobtained by applying a paste containing conductive particles. Theconductive particles contained in the fired electrode layer maypreferably be, for example, particles containing at least one of Cu, Ni,Ag, Pd, an Ag—Pd alloy, and Au.

The second electrode layer 14 b is provided on a surface of the firstelectrode layer 14 a. The second electrode layer 14 b may preferably bedefined by a plated layer. In the present preferred embodiment, thesecond electrode layer 14 b preferably is defined by a Ni plated layer.

The third electrode layer 14 c is provided on a surface of the secondelectrode layer 14 b. The third electrode layer 14 c may preferably bedefined by a plated layer. In the present preferred embodiment, thethird electrode layer 14 c is preferably defined by a Sn plated layer.

The electronic component 1 further includes a water-repellent film 20.The water-repellent film 20 is a solid of a polymer containing anon-cross-linked silicone resin but not containing a cross-linkingagent. The water-repellent film 20 may be defined by only anon-cross-linked silicone resin or may be defined by a resin compositioncontaining a filler, for example.

The non-cross-linked silicone resin is preferably made of a siliconeoligomer or a silicone polymer not containing a cross-linking agent, andfurther preferably made of a solution in which a silicone polymer isdispersed in an organic solvent. As a silicone oligomer or a siliconepolymer not containing a cross-linking agent, for example, a materialhaving a trade name such as FZ-3704, BY16-846, SF8416, SH203, 230FLUID,SF8419, and SF8422 (all of which are manufactured by Dow Corning Toray),XC96-B0446, XR31-B1410, XR31-B2230, and XC96-C2813 (all of which aremanufactured by Momentive Performance Materials Japan LLC), and KC-89S,KR-500, X-40-9225, X-40-9246, X-40-9250, KR-9218, K213, and KR-510 (allof which are manufactured by Shin-Etsu Chemical Co., Ltd.) can be usedalone or in combination. A preferable filler is exemplified by silicaparticles, for example.

The water-repellent film 20 is provided on another portion of thesurface of the electronic component main body 10 (on a surface of anexposed portion where the first and second external electrodes 13 and 14are not provided) and on a surface of at least one of the first andsecond external electrodes 13 and 14. Thus, the formation of a waterfilm on the electronic component main body 10 is significantly reducedor prevented. Therefore, the occurrence of ion migration issignificantly reduced or prevented.

Ion migration accompanies ionization of a metallic component in anexternal electrode and migration of the ionized metallic component to anopposing electrode. Therefore, contact between the external electrodeand moisture is preferably prevented so as to prevent the occurrence ofion migration. Accordingly, in order to more effectively prevent theoccurrence of ion migration, the water-repellent film 20 preferablycovers at least a portion of the first and second external electrodes 13and 14. The water-repellent film 20 more preferably covers the tip endportions of the first and second external electrodes 13 and 14. Thewater-repellent film 20 further preferably extends across the surface ofat least one of the first and second external electrodes 13 and 14 andthe surface of the electronic component main body 10.

In order to prevent ions generated at one of the first and secondexternal electrodes 13 and 14 from reaching the other of the externalelectrodes, the water-repellent film 20 is preferably provided on atleast one of the first and second main surfaces 10 a and 10 b and thefirst and second side surfaces 10 c and 10 d, so as to separate thefirst external electrode 13 and the second external electrode 14 fromeach other.

The water-repellent film 20 further preferably covers the entire surfaceof the exposed portion of the electronic component main body 10 and thefirst and second external electrodes 13 and 14. Here, thewater-repellent film 20 covering the entire surface of the exposedportion of the electronic component main body 10 and the first andsecond external electrodes 13 and 14 indicates that the water-repellentfilm 20 covers about 90% or more of the entire surface of the exposedportion of the electronic component main body 10 and the first andsecond external electrodes 13 and 14. For example, in a case in whichthe water-repellent film 20 is made of a silicone resin, when theexposed portion of the electronic component main body 10 and the firstand second external electrodes 13 and 14 are subjected to Si mapping ina field of view of about 50 μm² with the use of time-of-flight secondaryion mass spectrometry (TOF-SIMS), ions including Si are detected from aportion covered with the water-repellent film 20. Namely, thewater-repellent film 20 covering the entire surface of the exposedportion of the electronic component main body 10 and the first andsecond external electrodes 13 and 14 indicates that, in an analysis withTOF-SIMS, ions including Si are detected in a portion occupying about90% or more of the entire surface of the exposed portion of theelectronic component main body 10 and the first and second externalelectrodes 13 and 14.

FIG. 3 is a cross-sectional view of a mount structure of an electroniccomponent according to the first preferred embodiment of the presentinvention. As shown in FIG. 3, a mount structure 2 of the electroniccomponent includes the electronic component 1, a mount substrate 30, andsolder 32. The electronic component 1 is mounted on the mount substrate30. A land 31 provided on a mount surface 30 a of the mount substrate 30and the first and second external electrodes 13 and 14 are joined toeach other by solder 32. A solder member 32 (for example, a solder ball)includes solder and a solder flux. The solder flux contains a solvent.The solvent contained in the solder flux may be an aqueous solvent or anorganic solvent.

For example, when a surface of the electronic component main body ismodified with a cross-linked silane coupling agent, there is an upperlimit to an amount of the silane coupling agent per unit area with whichthe surface can be modified. In particular, as a water-repellent grouphaving a long straight chain is introduced in order to obtain anexcellent liquid repellent property, steric hindrance between adjacentsilane coupling agents is more significant, and thus, an amount ofsilane coupling agent per unit area with which the surface of theelectronic component main body can be modified decreases. Therefore, itis difficult to modify the surface densely with the silane couplingagent having a water-repellent group with a long straight chain.

Specifically, as a straight chain of a water-repellent group of thesilane coupling agent is increased in length, steric hindrance is moresignificant and repulsive force between straight chains of the silanecoupling agent is increased. Therefore, since an interval between thestraight chains of the silane coupling agent inevitably increases, thecapability to cover an electrode portion is reduced, moisture producedby condensation is more likely to form a water film, and ion migrationmay occur through the generation process described above.

Since a treatment film formed with the silane coupling agent is providedon a surface of an electronic component in a state of an elementarysubstance (a monomer) having one Si (silicon) atom, a portion wheremonomers are not bonded to each other is produced. Therefore, it isdifficult for the treatment film defined by the silane coupling agent tohave a dense film structure. Accordingly, it is difficult to provide adense water-repellent film if a surface of an electronic component mainbody is modified with a silane coupling agent.

International Publication WO2002/082480 proposed a method of providinghigh water repellency by using a silane coupling agent including F(fluorine) in a functional group. With this method, the length of astraight chain of a silane coupling treatment film can be reduced.However, even with the silane coupling treatment, there is a portionwhere bonding between silicon and silicon is insufficient. Thus, thecapability to cover an electrode portion is insufficient in a silanecoupling treatment film including F (fluorine) in a functional group,and resistance to ion migration cannot sufficiently be produced. Amolecular weight of a water-repellent film including a cross-linkedsilane coupling agent is undesirably high. Therefore, it becomesdifficult for the water-repellent film to be dissolved in a solventcontained in a solder flux. Therefore, when a water-repellent filmincludes a cross-linked silane coupling agent, the mountability of anelectronic component is reduced.

In the electronic component 1, a water-repellent film 20 containing anon-cross-linked silicone resin is provided. This is because, by using awater-repellent film containing a non-cross-linked silicone resin as thewater-repellent film 20, unlike a cross-linked silane coupling treatmentfilm, no cross-linking reaction occurs during film formation, and thus,control of the number of repeating units in siloxane bond is facilitatedand a molecular weight of a treatment agent is prevented fromundesirably increasing. Thus, a problem in that the water-repellent film20 is not dissolved in a solvent contained in a solder flux and themountability of an electronic component being reduced are avoided, and adense treatment film is provided. A water-repellent film containing anon-cross-linked silicone resin is preferably composed of a polymerconstituted of such siloxane bond as being expressed as —Si—O—Si, andsilicon is connected to form a high-polymer structure in a chain orlump. Therefore, a water-repellent film containing a non-cross-linkedsilicone resin has a dense structure. Thus, the water-repellent film 20is denser and more water-repellent than a water-repellent film includinga cross-linked silane coupling agent. Therefore, by providing thewater-repellent film 20, as compared to a water-repellent film includinga silane coupling agent, the occurrence of ion migration is effectivelyreduced or prevented.

Whether a water-repellent film is of a cross-linked type or anon-cross-linked type can be determined by heating a treatment agentused for the water-repellent film under a condition, for example, ofabout 150° C. for about 30 minutes and checking a molecular weight.Here, the determination of a non-cross-linked water-repellent film canbe made when no increase in molecular weight as compared to a molecularweight before heating is observed.

However, the inventors of the present invention have unexpectedlydiscovered that the occurrence of ion migration cannot sufficiently bereduced or prevented in some cases even when the water-repellent film 20containing a non-cross-linked silicone resin is provided. The inventorsof the present invention have conducted further dedicated studies, andhave surprisingly and unexpectedly discovered that, when an angle ofcontact of a water-repellent film with water of about 25° C. isincreased, from a certain angle, an effect of reducing or preventing theoccurrence of ion migration is drastically improved.

Then, in the present preferred embodiment, the water-repellent film 20is provided such that an angle of contact (a static angle of contact) ofwater of about 25° C. with the water-repellent film 20 is not less thanabout 100° and not greater than about 160°, for example. Thus, theoccurrence of ion migration is effectively reduced or prevented.

An angle of contact of water of about 25° C. with the water-repellentfilm 20 can be measured, for example, in the following manner, with theuse of a microscopic contact angle meter (MCA-3 manufactured by KyowaInterface Science Co., Ltd.). Initially, an electronic component isarranged on a horizontal base such that a second main surface faces thebase. Then, an angle of contact of water of about 25° C. with thewater-repellent film 20 can be determined by dropping water droplets atabout 25° C. onto the water-repellent film 20 on a first main surface ofthe electronic component of which surface temperature is about 25° C. inan environment in which an ambient temperature of the electroniccomponent is set to about 25° C., and thereafter photographing a waterfilm formed on the main surface in a lateral direction. This angle ofcontact is a static angle of contact measured immediately afterdropping.

As described above, in order to reduce or prevent the occurrence of ionmigration, a water-repellent film is preferably also provided on asurface of at least one of the first and second external electrodes.However, as a result of dedicated studies conducted by the inventors ofthe present invention, it has been discovered that the mountability ofan electronic component reduces when a water-repellent film includes across-linked silane coupling agent described in InternationalPublication WO2002/082480. This is because, though treatment with asilane coupling agent containing fluorine (a perfluoroalkyl group) isperformed in the technique described in International PublicationWO2002/082480, fluorine has oil repellence and repels a flux in a solderpaste, which has led to reduced wettability of solder during mountingand reduced mount ability.

In contrast, in the electronic component 1, the water-repellent film 20contains a non-cross-linked silicone resin. The non-cross-linkedsilicone resin does not have oil repellence and blends well with a fluxin a solder paste. In addition, unlike the silane coupling agent, thenon-cross-linked silicone resin is not directly coupled to the first andsecond external electrodes 13 and 14. Therefore, since thewater-repellent film 20 is dissolved in a solvent contained in a solderflux during mounting, it is readily removed from the surface of thefirst and second external electrodes 13 and 14. Accordingly, a soldermelt and the first and second external electrodes 13 and 14 tend to bein direct contact with each other. Thus, the first and second externalelectrodes 13 and 14 and the solder 32 are suitably joined to eachother. Therefore, the electronic component 1 has excellent mountability.

In the present preferred embodiment, an example in which the firstexternal electrode 13 extends across the surface of the first endsurface 10 e and the surface of each of the first and second mainsurfaces 10 a and 10 b and the first and second side surfaces 10 c an 10d is described. An example in which the second external electrode 14extends across the surface of the second end surface 10 f and thesurface of each of the first and second main surfaces 10 a and 10 b andthe first and second side surfaces 10 c an 10 d is described. Thearrangement of the first and second external electrodes is not limitedto the above-described arrangement, and for example, the first andsecond external electrodes may be provided only on the first and secondend surfaces 10 e and 10 f of the electronic component main body 10. Thefirst and second external electrodes may be provided only on the secondmain surface 10 b of the electronic component main body 10. The firstand second external electrodes may extend across the surfaces of thefirst and second end surfaces 10 e and 10 f and the surface of secondmain surface 10 b of the electronic component main body 10. In thepresent preferred embodiment, an example in which an electroniccomponent includes two external electrodes is described. The presentpreferred embodiment is not limited thereto, and an electronic componentmay include three or more external electrodes.

A method of manufacturing the electronic component 1 is not particularlylimited. The electronic component 1 can be manufactured, for example, inthe following manner. Initially, the electronic component main body 10including the first and second internal electrodes 11 and 12 isprepared. The electronic component main body 10 can be manufactured witha known method. Specifically, the electronic component main body 10 canbe manufactured, for example, in the following manner. Initially, aceramic green sheet is prepared. Then, a conductive paste layer isformed by printing a conductive paste on the ceramic green sheet. Then,after a plurality of ceramic green sheets not including a conductivepaste layer printed thereon are stacked, a ceramic green sheet includinga conductive paste printed is stacked, and further thereon, a ceramicgreen sheet including a conductive paste layer printed thereon isstacked. A mother stack is thus fabricated. The mother stack may bepressed with isostatic pressing. Then, by cutting and dividing themother stack in a plurality of pieces, a plurality of soft ceramicelements are fabricated. Then, the electronic component main body 10 canbe completed by firing the soft ceramic elements.

Then, the first and second external electrodes 13 and 14 are formed onthe surface of the electronic component main body 10. The first andsecond external electrodes 13 and 14 can be formed, for example, in thefollowing manner. The first electrode layers 13 a and 14 a are formed byapplying a conductive paste onto a portion of the surface of theelectronic component main body 10 and baking the conductive paste. Thesecond electrode layers 13 b and 14 b are formed on the surface of thefirst electrode layers 13 a and 14 a by providing Ni plating. The thirdelectrode layers 13 c and 14 c are formed on the surface of the secondelectrode layers 13 b and 14 b by providing Sn plating. Through thesteps described above, the first and second external electrodes 13 and14 are formed.

Then, the water-repellent film 20 is formed on another portion of thesurface of the electronic component main body 10 and the surface of thefirst and second external electrodes 13 and 14. Specifically, initially,a treatment agent is prepared by diluting a resin for forming thewater-repellent film 20 with a solvent such as an alkane-based solvent,an isoparaffin-based solvent, or a xylene-based solvent. Thewater-repellent film 20 can be formed by immersing the electroniccomponent main body 10 including first and second external electrodes 13and 14 formed thereon in the treatment agent, followed by drying.Alternatively, a treatment agent may be applied to the electroniccomponent main body 10 including first and second external electrodes 13and 14 formed thereon. A concentration of a resin in a treatment agentis preferably, for example, not lower than about 1 mass % and not higherthan about 50 mass %, more preferably not lower than about 3 mass % andnot higher than about 50 mass %, and further preferably not lower thanabout 3 mass % and not higher than about 10 mass %. A time period ofimmersion in the treatment agent is, for example, approximately notshorter than about 1 minute and not longer than about 10 minutes.Regarding conditions for drying, for example, the electronic componentmain body is held, for example, at a temperature approximately not lowerthan about 100° C. and not higher than about 200° C. during a periodapproximately not shorter than 10 minutes and not longer than about 60minutes.

An angle of contact of the water with water-repellent film 20 can becontrolled, for example, by adjusting a material used for thewater-repellent film 20 or a thickness of the water-repellent film 20.Normally, as the thickness of the water-repellent film 20 increases, aninfluence caused by underlying ceramics is less likely and, thus, anangle of contact of water with the water-repellent film 20 tends to begreater. A thickness of the water-repellent film 20 can be controlled,for example, by adjusting a concentration of a water-repellent resin ina treatment agent. Specifically, a thickness of water-repellent film 20can be adjusted by using a treatment solution in which a concentrationof a non-cross-linked resin is from about 1 mass % to about 60 mass %.

An Experimental Example 1 in which the influence of an angle of contactbetween water of about 25° C. and a water-repellent film on each ofwhether or not ion migration in an electronic component occurs and themountability of an electronic component will be described below.

Experimental Example 1

In Experimental Example 1, nine types of electronic components and mountstructures of the electronic components in Example 1 to Example 5 andComparative Example 1 to Comparative Example 4 were fabricated. A stackceramic capacitor was fabricated as the electronic component.

Example 1

An electronic component and a mount structure of the electroniccomponent according to Example 1 substantially the same as theelectronic component 1 according to the first preferred embodiment werefabricated under the conditions described below. A dimension (a designvalue) of the electronic component was set to about 1.6 mm in length,about 0.8 mm in width, and about 0.8 mm in thickness. A ceramic portionwas composed of BaTiO₃. The first and second internal electrodes 11 and12 were composed of Ni. The first electrode layers 13 a and 14 a wereformed from a fired electrode layer containing Cu. The second electrodelayers 13 b and 14 b were formed from a Ni plated layer. The thirdelectrode layers 13 c and 14 c were formed from a Sn plated layer. Adistance along the length direction between the first external electrode13 and the second external electrode 14 in each of the first and secondmain surfaces 10 a and 10 b was set to about 0.8 mm. A liquid obtainedby diluting a silicone polymer dispersion liquid containing anon-cross-linked silicone resin (SD-8002 DISPERSION manufactured by DowCorning Toray) such that a concentration of the non-cross-linkedsilicone resin was about mass % was used as a treatment solution. Forforming the water-repellent film 20, after the electronic component mainbody 10 including the first and second external electrodes 13 and 14 wasimmersed in the treatment solution for about 5 minutes, the electroniccomponent main body was taken out of the treatment solution and dried atabout 150° C. for about 30 minutes. Consequently, a water-repellent filmhaving a thickness of approximately 5 nm was formed. The mount structureof the electronic component was fabricated by solder-mounting theelectronic component on a substrate with the use of solder (96.5 Sn-3Ag-0.5 Cu paste, M705-GRN360-K2-V manufactured by Senju Metal IndustryCo., Ltd.).

Example 2

An electronic component and a mount structure of the electroniccomponent according to Example 2 were fabricated as in Example 1 exceptthat a concentration of the non-cross-linked silicone resin in thetreatment solution was set to about 5 mass %. The formed water-repellentfilm had a thickness of approximately 50 nm.

Example 3

An electronic component and a mount structure of the electroniccomponent according to Example 3 were fabricated as in Example 1 exceptthat a concentration of the non-cross-linked silicone resin in thetreatment solution was set to about 20 mass %. The formedwater-repellent film had a thickness of approximately 100 nm.

Example 4

An electronic component and a mount structure of the electroniccomponent according to Example 4 were fabricated as in Example 1 exceptthat a concentration of the non-cross-linked silicone resin in thetreatment solution was set to about 40 mass %. The formedwater-repellent film had a thickness of approximately 200 nm.

Example 5

A non-cross-linked silicone resin (SD-8002 DISPERSION manufactured byDow Corning Toray) was diluted with isoparaffin such that aconcentration of the non-cross-linked silicone resin was about 5 mass %.A dispersion liquid was prepared by adding about 1.0 mass % ofhydrophobic fumed silica (RX50 manufactured by Nippon Aerosil Co., Ltd.and having a BET specific surface area of 35 m²/g) to the liquidresulting from dilution and dispersing silica with the use of anultrasonic homogenizer. An electronic component and a mount structure ofthe electronic component according to Example 5 were fabricated as inExample 1 except that a water-repellent film was formed by using thisdispersion liquid as a treatment solution. The formed water-repellentfilm had a thickness of approximately 5 nm.

Comparative Example 1

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 1 were fabricated as inExample 1 except that no water-repellent film was formed.

Comparative Example 2

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 2 were fabricated as inExample 1 except that a concentration of the non-cross-linked siliconeresin in the treatment solution was set to about 0.1 mass %.

Comparative Example 3

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 3 were fabricated as inExample 1 except that a water-repellent film was formed with the use ofa treatment solution obtained by diluting an alkoxysilane-based silanecoupling agent (KBM-3063 manufactured by Shin-Etsu Chemical Co., Ltd.)with propanol to about 5 volume %.

Comparative Example 4

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 4 were fabricated as inExample 1 except that a water-repellent film was formed with the use ofa treatment solution made of a fluorine-based silane coupling agent.

A measurement method and an evaluation method in the presentExperimental Example will be described below.

Method of Measuring Thickness

A method of measuring a thickness of a water-repellent film in a sampleelectronic component fabricated in each of Examples 1 to 5 andComparative Examples 1 to 4 was performed as follows. Initially, in amain surface opposite to a mount surface of the electronic component (anLW surface), a cross-section of a water-repellent film was partiallyexposed by using a focused ion beam (FIB) emitted under a condition ofan angle of about 45° with respect to a vertical direction such that aprocess range extending, starting from a central position in the widthdirection W and a central position in the length direction L (a portioncircled in FIG. 2) of one external electrode along the length directionL formed on the LW surface, by about 30 μm along the length direction Ltoward the other external electrode and by about 30 μm along thethickness direction T is obtained. Then, a water-repellent film at thecentral position in the length direction L of the water-repellent filmwhich was exposed at the exposed cross-section was projected with SEMand a thickness thereof was measured. The measurement value was adoptedas a thickness of the water-repellent film.

Measurement of Angle of Contact

Tables 1 and 2 show results of a measurement of an angle of contact ofwater of about 25° C. with the water-repellent film in the sampleelectronic component fabricated in each of Examples 1 to 5 andComparative Examples 2 to 4. In Comparative Example 1 where nowater-repellent film was formed, an angle of contact of water of about25° C. with a main surface of the electronic component main body wasmeasured. Table 1 shows results, with samples having achieved a targetvalue being extracted from among a plurality of samples which had beenfabricated to aim at each angle of contact shown in Table 1.

Evaluation of Ion Migration

A cycle test for condensation in the mount structure of the electroniccomponent in each of Examples 1 to 5 and Comparative Examples 1 to 4 wasconducted under the following conditions. The fabricated mount structureof the electronic component was held for about 1 hour in an environmentat a temperature as low as about −30° C. Thereafter, the mount structurewas held for about 1 hour in an environment at a high temperature ofabout 25° C. and a high humidity of about 90%. Finally, the mountstructure of the electronic component was dried while about 1.5 hourelapsed to lower humidity to about 50% at a temperature of about 25° C.This process was defined as 1 cycle and 48 cycles were carried out.

Thereafter, a portion of the second main surface was observed as beingmagnified by 100 times with the use of a microscope. Consequently, acase in which the presence of a white or black product was observed onthe second main surface was determined as an occurrence of ion migrationor “bad”. A case in which a white or black product was not observed onthe second main surface was evaluated as an absence of an occurrence ofion migration or “good”. Tables 1 and 2 show a ratio of the number ofsamples determined as “bad” to the total number of samples ((the numberof samples determined as “bad”)/(the total number of samples)). Here,the number of tested samples was set to n=18.

Sn, Ni, or Cu could be detected as a result of analysis of a productwith a wavelength-dispersive X-ray spectrometer (WDX). Therefore, theobserved white or black product was confirmed as a product resultingfrom ion migration.

Evaluation of Mountability

Mountability of the sample mount structure of the electronic componentfabricated in each of Examples 1 to 5 and Comparative Examples 1 to 4was evaluated with the use of a solder wettability tester “SAT-5100manufactured by Rhesca Corporation” in accordance with JIS C 60068-2-69“Environmental testing-Part 2-69: Tests-Test Te: Solderability testingof electronic components for surface mounting devices (SMD) by thewetting balance method.”

Specifically, the electronic component was mounted on a glass epoxysubstrate with unleaded solder (96.5 Sn-3 Ag-0.5 Cu). A solder pelletmanufactured by Rhesca Corporation was used as the solder. A solution ofabout 25% of solid rosin (pine resin) and about 75% of isopropyl alcohol(IPA) (a weight ratio) was used as a flux. A temperature for the testwas set to about 245° C. Based on the obtained test results, a sample ofwhich zero crossing time (representing a time at which wetting starts)was within about 1.5 second was evaluated as “good” and a sample ofwhich zero crossing time was equal to or greater than about 1.5 secondwas evaluated as “bad”. Table 1 shows a ratio of the number of samplesdetermined as “bad” to the total number of samples ((the number ofsamples determined as “bad”)/(the total number of samples)). Here, thenumber of tested samples was set to n=10.

TABLE 1 Static Contact Angle Between Ratio of Water-Repellent OccurrenceRatio of Film and of Ion Defective Water at 25° C. (°) MigrationMountability Comparative 82 18/18  0/10 Example 1 Comparative 95 9/180/10 Example 2 Example 1 100 2/18 0/10 Example 2 110 0/18 0/10 Example 3120 1/18 0/10 Example 4 130 1/18 0/10 Example 5 160 0/18 0/10

TABLE 2 Static Contact Angle Between Ratio of Water-Repellent OccurrenceRatio of Film and of Ion Defective Water at 25° C. (°) MigrationMountability Comparative 93 16/18 10/10 Example 3 Comparative 160  8/1810/10 Example 4

As shown in Table 1, a ratio of the occurrence of ion migrationdrastically changed, with an angle of contact of about 100° of water ofabout 25° C. with the water-repellent film defining a threshold. Itcould be confirmed from the results in the present Experimental Examplethat the occurrence of ion migration could suitably be reduced orprevented by setting an angle of contact of water of about 25° C. withthe water-repellent film to about 100° or greater.

As shown in Table 2, when the water-repellent film was formed with thesilane coupling agent, the occurrence of ion migration could not besufficiently reduced or prevented even though an angle of contact ofwater of about 25° C. with the water-repellent film was set to about100° or greater. It was discovered therefrom that the formation of awater-repellent film, of which the angle of contact of water of about25° C. with the water-repellent film is about 100° or greater, with theuse of a non-cross-linked silicone resin was important for effectivereduction or preventions of the occurrence of ion migration. Inaddition, as shown in Table 2, mountability was not satisfactory when awater-repellent film was formed of a cross-linked silane coupling agent.

It was confirmed from the results described above that, by forming awater-repellent film, of which the angle of contact with water of about25° C. was not less than about 100° and not greater than about 160°,with the use of a non-cross-linked silicone resin, the occurrence of ionmigration could effectively be reduced or prevented and excellentmountability could be obtained.

An electronic component, a method of manufacturing the same, and a mountstructure of the electronic component according to a second preferredembodiment of the present invention will be described below. Since theelectronic component, the method of manufacturing the same, and themount structure of the electronic component according to the presentpreferred embodiment are different from the electronic component, themethod of manufacturing the same, and the mount structure of theelectronic component according to the first preferred embodiment in thatthe occurrence of ion migration is reduced or prevented and goodmountability with solder is achieved by defining a weight-averagemolecular weight of a non-cross-linked silicone resin contained in awater-repellent film, description of features the same as or similar tothose in the first preferred embodiment will not be repeated.

Second Preferred Embodiment

In the second preferred embodiment of the present invention, awater-repellent film is provided such that an angle of contact (a staticangle of contact) of water of about 25° C. with the water-repellent filmis not less than about 90°, for example. A non-cross-linked siliconeresin contained in the water-repellent film has a weight-averagemolecular weight not less than about 7400 g/mol and not more than about8000 g/mol, for example.

An Experimental Example 2 in which the influence of a weight-averagemolecular weight of a non-cross-linked silicone resin on each of whetheror not ion migration in an electronic component occurs and mountabilityof an electronic component will be described below.

Experimental Example 2

In Experimental Example 2, six types of electronic components and mountstructures of the electronic components in Example 6 to Example 8 andComparative Example 5 to Comparative Example 7 were fabricated. Astacked ceramic capacitor was fabricated as the electronic component.

Example 6

An electronic component and a mount structure of the electroniccomponent according to Example 6 substantially the same as theelectronic component according to the second preferred embodiment werefabricated under the conditions described below. A dimension (a designvalue) of the electronic component was set to about 1.6 mm in length,about 0.8 mm in width, and about 0.8 mm in thickness. A ceramic portionwas composed of BaTiO₃. The first and second internal electrodes werecomposed of Ni. The first electrode layer was made of a fired electrodelayer containing Cu. The second electrode layer was made of a Ni platedlayer. The third electrode layer was made of a Sn plated layer. Adistance along the length direction between the first external electrodeand the second external electrode in each of the first and second mainsurfaces was set to about 0.8 mm. A liquid obtained by diluting asilicone polymer dispersion liquid (SD-8002 DISPERSION manufactured byDow Corning Toray) containing a non-cross-linked silicone resin having aweight-average molecular weight not less than about 7400 g/mol and notmore than about 8000 g/mol such that a concentration of thenon-cross-linked silicone resin was about 1 mass % was used as thetreatment solution. For forming a water-repellent film, after theelectronic component main body 10 including the first and secondexternal electrodes was immersed in the treatment solution for about 5minutes, the electronic component main body was taken out of thetreatment solution and dried at about 150° C. for about 30 minutes.Consequently, a water-repellent film having a thickness of approximately5 nm was formed. The mount structure of the electronic component wasfabricated by solder-mounting the electronic component on a substratewith the use of solder (96.5 Sn-3 Ag-0.5 Cu paste, M705-GRN360-K2-Vmanufactured by Senju Metal Industry Co., Ltd.).

Example 7

An electronic component and a mount structure of the electroniccomponent according to Example 7 were fabricated as in Example 6 exceptthat a concentration of the non-cross-linked silicone resin in thetreatment solution was set to about 5 mass %. The water-repellent filmhad a thickness of approximately 50 nm.

Example 8

An electronic component and a mount structure of the electroniccomponent according to Example 8 were fabricated as in Example 6 exceptthat a concentration of the non-cross-linked silicone resin in thetreatment solution was set to about 60 mass %. The formedwater-repellent film had a thickness of approximately 250 nm.

Comparative Example 5

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 5 were fabricated as inExample 6 except that no water-repellent film was formed.

Comparative Example 6

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 6 were fabricated as inExample 6 except that a water-repellent film was formed with the use ofa treatment solution obtained by diluting an alkoxysilane-based silanecoupling agent (KBM-3063 manufactured by Shin-Etsu Chemical Co., Ltd.)with propanol to 5 volume %.

Comparative Example 7

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 7 were fabricated as inExample 6 except that a water-repellent film was formed with the use ofa silicone-based cross-linked polymer coating liquid (KR-400manufactured by Shin-Etsu Chemical Co., Ltd.). The formedwater-repellent film had a thickness of approximately 5 μm.

A measurement method and an evaluation method in the presentExperimental Example will be described below. Ion migration andmountability were evaluated as in Experimental Example 1.

Measurement of Weight-Average Molecular Weight

In each of Examples 6 to 8 and Comparative Example 6, three thousandsamples were created. Three thousand samples were immersed inisoparaffin to thereby dissolve the water-repellent film in isoparaffin.To 10 g of tetrahydrofuran, 0.02 g of the isoparaffin solution in whichthe water-repellent film had been dissolved was added. Tetrahydrofuranto which the isoparaffin solution had been added was analyzed with ahigh performance liquid chromatograph (HPLC manufactured by ShimadzuCorporation) with a measurement mode being set to size exclusionchromatography (SEC), and a weight-average molecular weight was measuredbased on a result thereof.

Table 3 shows results of measurements of a weight-average molecularweight of the non-cross-linked silicone resin in the sample electroniccomponent fabricated in each of Example 6 to Example 8 and ComparativeExamples 6 and 7. In the sample fabricated in Comparative Example 7, thewater-repellent film was not dissolved in isoparaffin. Therefore, aweight-average molecular weight of the water-repellent film of thesample electronic component according to Comparative Example 7 could notbe measured.

TABLE 3 Weight-Average Ratio of Molecular Weight of Occurrence Ratio ofNon-Cross-Linked of Ion Defective Silicone Resin (g/mol) MigrationMountability Example 6 7400 0/18 0/10 Example 7 8000 0/18 0/10 Example 87800 0/18 0/10 Comparative — 18/18  0/10 Example 5 Comparative 26016/18  0/10 Example 6 Comparative — 0/18 10/10  Example 7

As shown in Table 3, it was confirmed that, when a weight-averagemolecular weight of the non-cross-linked silicone resin was within arange not less than about 7400 g/mol and not more than about 8000 g/mol,the occurrence of ion migration was not observed, and the occurrence ofion migration was effectively reduced or prevented and excellentmountability was obtained. In the electronic component according toComparative Example 7, the occurrence of ion migration was not observed,however, mountability was not satisfactory.

An electronic component, a method of manufacturing the same, and a mountstructure of the electronic component according to a third preferredembodiment of the present invention will be described below. Theelectronic component, the method of manufacturing the same, and themount structure of the electronic component according to the presentpreferred embodiment achieve good mountability with solder while theoccurrence of ion migration is reduced or prevented, by providing awater-repellent film soluble in a solvent contained in a solder flux oran organic solvent. Description of features the same as or similar tothose in the first preferred embodiment or the second preferredembodiment will not be repeated.

Third Preferred Embodiment

In the third preferred embodiment of the present invention, awater-repellent film is preferably composed, for example, of a resin. Awater-repellent film is preferably composed, for example, of a siliconeresin or a fluorine-based resin. A resin included in a water-repellentfilm is preferably a non-cross-linked resin. A non-cross-linked resindoes not produce cross-linking reaction. With a non-cross-linked resin,a molecular weight of a resin is readily be controllable and a molecularweight is prevented from undesirably increasing. Therefore, awater-repellent film hardened by drying a non-cross-linked resin issoluble in an organic solvent or a solvent contained in a solder flux. Awater-repellent film may be composed, for example, only of resin, or maybe composed of a resin composition containing a filler. Awater-repellent film is formed such that an angle of contact (a staticangle of contact) of water of about 25° C. with the water-repellent filmis not less than about 100°.

A solder member forming solder included in the mount structure of theelectronic component includes solder and a solder flux. The solder fluxcontains a solvent. The solvent contained in the solder flux may be anaqueous solvent or an organic solvent. A preferred organic solvent isexemplified by an organic solvent including at least one selected fromthe group consisting of an ether-based organic solvent, an alcohol-basedorganic solvent, a hydrocarbon-based organic solvent, a ketone-basedorganic solvent, an ester-based organic solvent, and aglycol-ether-based organic solvent. A solubility parameter (an SP value)of the solvent contained in the solder flux is preferably, for example,from about 7.0 to about 14.0.

In the present preferred embodiment, a water-repellent resin soluble ina solvent contained in a solder flux is used for a water-repellent film.By using a solvent closer in solubility parameter (SP value) to thesolvent contained in the solder flux as a solvent for diluting a resinfor forming the water-repellent film, a highly homogenous treatmentagent is provided. Therefore, a water-repellent film high in homogeneityis manufactured. The water-repellent film is soluble in the solventcontained in the solder flux during mounting of an electronic component.Therefore, when an electronic component is mounted, the water-repellentfilm located on a surface of a portion of the first and second externalelectrodes joined by solder is removed. Thus, no water-repellent film isprovided at an interface between the first and second externalelectrodes and the solder in the mount structure of the electroniccomponent. That is, no water-repellent film is provided at a junctionbetween the electronic component and the mount substrate. Accordingly,direct contact between a solder melt and the first and second externalelectrodes is likely to occur. Thus, the first and second externalelectrodes and solder are suitably joined to each other. Therefore, theelectronic component has excellent mount ability.

An Experimental Example 3 in which an influence of solubility of awater-repellent film in a solvent contained in a solder flux on each ofwhether or not ion migration in an electronic component occurs andmountability of an electronic component will be described below.

Experimental Example 3

In Experimental Example 3, seven types of electronic components andmount structures of the electronic components in Example 9 to Example 12and Comparative Example 8 to Comparative Example 10 were fabricated. Astacked ceramic capacitor was fabricated as the electronic component.

Example 9

An electronic component and a mount structure of the electroniccomponent according to Example 9 substantially the same as theelectronic component according to the third preferred embodiment werefabricated under the conditions below. A dimension (a design value) ofthe electronic component was set to about 1.6 mm in length, about 0.8 mmin width, and about 0.8 mm in thickness. A ceramic portion was composedof BaTiO₃. The first and second internal electrodes were composed of Ni.The first electrode layer was made of a fired electrode layer containingCu. The second electrode layer was made of a Ni plated layer. The thirdelectrode layer was made of a Sn plated layer. A distance along thelength direction between the first external electrode and the secondexternal electrode in each of the first and second main surfaces was setto about 0.8 mm. A liquid obtained by diluting a silicone polymerdispersion liquid containing a non-cross-linked silicone resin (SD-8002DISPERSION manufactured by Dow Corning Toray) such that a concentrationof the non-cross-linked silicone resin was about 1 mass % was used asthe treatment solution. For forming a water-repellent film, after theelectronic component main body 10 including the first and secondexternal electrodes was immersed in the treatment solution for about 5minutes, the electronic component main body was taken out of thetreatment solution and dried at about 150° C. for about 30 minutes.Consequently, a water-repellent film having a thickness of several nmwas formed. The mount structure of the electronic component wasfabricated by solder-mounting the electronic component on a substratewith the use of solder (96.5 Sn-3 Ag-0.5 Cu paste, M705-GRN360-K2-Vmanufactured by Senju Metal Industry Co., Ltd.).

Example 10

An electronic component and a mount structure of the electroniccomponent according to Example 10 were fabricated as in Example 9 exceptthat a concentration of the non-cross-linked silicone resin in thetreatment solution was set to about 5 mass %.

Example 11

An electronic component and a mount structure of the electroniccomponent according to Example 11 were fabricated as in Example 9 exceptthat a concentration of the non-cross-linked silicone resin in thetreatment solution was set to about 60 mass %.

Example 12

An electronic component and a mount structure of the electroniccomponent according to Example 12 were fabricated as in Example 9 exceptthat a water-repellent film was formed of a fluorine-basednon-cross-linked resin coating liquid (WOP-019XPC manufactured by NodaScreen Co., Ltd.). The formed water-repellent film had a thickness ofseveral nm.

Comparative Example 8

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 8 were fabricated as inExample 9 except that no water-repellent film was formed.

Comparative Example 9

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 9 were fabricated as inExample 9 except that a water-repellent film was formed using atreatment solution obtained by diluting an alkoxysilane-based silanecoupling agent (KBM-3063 manufactured by Shin-Etsu Chemical Co., Ltd.)with propanol to about 5 volume %.

Comparative Example 10

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 10 were fabricated as inExample 9 except that a water-repellent film was formed using asilicone-based cross-linked polymer coating liquid (KR-400 manufacturedby Shin-Etsu Chemical Co., Ltd.). The formed water-repellent film had athickness of approximately 5 μm.

A measurement method and an evaluation method in the presentExperimental Example will be described below. Ion migration andmountability were evaluated as in Experimental Example 1.

Evaluation of Solubility in Solvent Contained in Solder Flux

Whether or not the water-repellent film in the electronic componentfabricated in each of Examples 9 to 12 and Comparative Examples 8 to 10was dissolved in the solvent contained in the solder flux was evaluated.A case in which the fabricated electronic component was immersed in asolder flux containing about 25% of rosin and about 75% of propanol(flux F manufactured by Sasaki Chemical Co., Ltd.) and thewater-repellent film was dissolved and removed was defined as “good” anda case in which no change was observed in the water-repellent film wasdefined as “bad”. Here, the number of tested samples was set to n=10.Table 4 shows results of the present experiment.

TABLE 4 Solubility of Water-Repellent Ratio of Film in SolventOccurrence Ratio of Contained in of Ion Defective Solder Flux MigrationMountability Example 9 good 0/18 0/10 Example 10 good 0/18 0/10 Example11 good 0/18 0/10 Example 12 good 0/18 0/10 Comparative — 18/18  0/10Example 8 Comparative bad 16/18  0/10 Example 9 Comparative Example 10bad 0/18 10/10 

As shown in Table 4, it was confirmed that the water-repellent filmcontaining a non-cross-linked silicone resin was dissolved in thesolvent contained in the solder flux. It was confirmed that, in theelectronic component including the water-repellent film dissolved in thesolvent contained in the solder flux, the occurrence of ion migrationwas not observed, and the occurrence of ion migration could effectivelybe reduced or prevented and excellent mountability was obtained. In theelectronic component according to Comparative Example 9, mountabilitywas satisfactory, however, the occurrence of ion migration was observed.In the electronic component according to Comparative Example 10, theoccurrence of ion migration was not observed, however, mountability wasnot satisfactory.

An electronic component, a method of manufacturing the same, and a mountstructure of the electronic component according to a fourth preferredembodiment of the present invention will be described below. Theelectronic component, the method of manufacturing the same, and themount structure of the electronic component according to the presentpreferred embodiment achieve good mountability with solder while theoccurrence of ion migration is effectively reduced or prevented, byproviding a water-repellent film defined by a silicone resin film havinga thickness not greater than about 200 nm. Description of features thesame as in the first to third preferred embodiments will not berepeated.

Fourth Preferred Embodiment

An electronic component according to the fourth preferred embodiment ofthe present invention includes a silicone resin film as awater-repellent film. The silicone resin film should only be a filmcontaining a silicone resin. The silicone resin may be formed, forexample, only of a silicone resin or of a silicone resin compositioncontaining a filler.

When the inventors of the present invention actually fabricated anelectronic component provided with a silicone resin film, in some cases,disadvantageously, electronic components adhered to each other when aplurality of electronic components were in contact with each other, andan electronic component was not detached from a suction and attractionmechanism when the electronic component was transported with the use ofthe suction and attraction mechanism. The inventors of the presentinvention discovered as a result of further dedicated studies that, bysetting a thickness of a silicone resin film to about 200 nm or less,the adhesiveness of an electronic component was reduced, the problemsdescribed above were solved, and the mountability of the electroniccomponent was improved.

In the electronic component according to the present preferredembodiment, a thickness of a silicone resin film preferably is set toabout 200 nm, for example. Therefore, an adhesion force of an electroniccomponent to another member is low. Accordingly, for example, adhesionof a plurality of electronic components to each other or difficulty indetachment thereof from a suction and attraction mechanism areeffectively prevented. In order to further reduce the adhesion force ofan electronic component to another member, a silicone resin film has athickness preferably not greater than about 100 nm, for example. Whenthe thickness of a silicone resin film is too small, the occurrence ofion migration may not be sufficiently reduced or prevented. Therefore,the silicone resin film has a thickness preferably not less than about 1nm. A thickness of a silicone resin film can be controlled, for example,by appropriately adjusting a concentration of a silicone resin in atreatment agent.

A silicone resin film can be formed, for example, in the followingmanner. Initially, a treatment agent is prepared by diluting a siliconeresin by adding a solvent such as a paraffin-based solvent thereto. Inthe treatment agent, a concentration of the silicone resin can be, forexample, from about 0.01 mass % to about 10 mass %. Then, an electroniccomponent main body including the first and second external electrodesprovided thereon is immersed in the treatment agent, for example, forapproximately 1 to 10 minutes. Thereafter, a silicone resin film can beformed, for example, by drying the electronic component main body in aheated atmosphere from about 100° C. to about 200° C. for approximately10 to 60 minutes, for example.

An Experimental Example 4 in which the influence of a thickness of asilicone resin film on each of whether or not ion migration in anelectronic component occurs and adhesive force of a water-repellent film(mountability of an electronic component) will be described below.

Experimental Example 4

In Experimental Example 4, six types of electronic components and mountstructures of the electronic components in Example 13 to Example 15 andComparative Example 11 to Comparative Example 13 were fabricated. Astacked ceramic capacitor was fabricated as the electronic component.

Example 13

An electronic component and a mount structure of the electroniccomponent according to Example 13 that are the same or substantially thesame as the electronic component according to the fourth preferredembodiment were fabricated under the conditions below. A dimension (adesign value) of the electronic component was set to about 1.6 mm inlength, about 0.8 mm in width, and about 0.8 mm in thickness. A ceramicportion was composed of BaTiO₃. The first and second internal electrodeswere composed of Ni. The first electrode layer was made of a firedelectrode layer containing Cu. The second electrode layer was made of aNi plated layer. The third electrode layer was made of a Sn platedlayer. A distance along the length direction between the first externalelectrode and the second external electrode in each of the first andsecond main surfaces was set to about 0.8 mm. A concentration of asilicone resin in a treatment solution was set to about 0.008 mass %.For forming the water-repellent film 20, immersion of the electroniccomponent main body including the first and second external electrodesprovided thereon in the treatment solution and drying thereof wererepeated seven times. A formed water-repellent film had a thickness ofabout 60 nm. The mount structure of the electronic component wasfabricated by solder-mounting the electronic component on a substratewith the use of solder (96.5 Sn-3 Ag-0.5 Cu paste, M705-GRN360-K2-Vmanufactured by Senju Metal Industry Co., Ltd.).

Example 14

An electronic component and a mount structure of the electroniccomponent according to Example 14 were fabricated as in Example 13except that a concentration of a silicone resin in the treatmentsolution was set to about 0.01 mass %. The water-repellent film had athickness of about 90 nm.

Example 15

An electronic component and a mount structure of the electroniccomponent according to Example 15 were fabricated as in Example 13except that a concentration of a silicone resin in the treatmentsolution was set to about 0.013 mass %. The water-repellent film had athickness of about 100 nm.

Comparative Example 11

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 11 were fabricated as inExample 13 except that a concentration of a silicone resin in thetreatment solution was set to about 0.042 mass %. The water-repellentfilm had a thickness of about 300 nm.

Comparative Example 12

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 12 were fabricated as inExample 13 except that a concentration of a silicone resin in thetreatment solution was set to about 0.057 mass %. The water-repellentfilm had a thickness of about 500 nm.

Comparative Example 13

An electronic component and a mount structure of the electroniccomponent according to Comparative Example 13 were fabricated as inExample 13 except that a water-repellent film was formed with the use ofa treatment solution obtained by diluting an alkoxysilane-based silanecoupling agent (KBM-3063 manufactured by Shin-Etsu Chemical Co., Ltd.)with propanol to about 10 volume %.

A measurement method and an evaluation method in the presentExperimental Example will be described below. A method of measuring athickness and evaluation of ion migration were the same as inExperimental Example 1.

Evaluation of Adhesive Force of Water-Repellent Film

Two electronic components fabricated in each of Examples 13 to 15 andComparative Examples 11 to 13 were sandwiched such that first mainsurfaces thereof were opposed to each other, a pressure of about 5N wasapplied thereto in a direction of a thickness thereof, and thereafter,the two electronic components were dropped onto a base from a height ofabout 2 cm above the base. A case in which the two electronic componentswere separated as a result of dropping was evaluated as low in adhesiveforce or “good”. A case in which the two electronic components were notseparated after dropping was evaluated as high in adhesive force or“bad”. This evaluation of adhesive force was conducted 100 times foreach of Examples 13 to 15 and Comparative Examples 11 to 13. Table 5shows the number of times of evaluation as “bad” in evaluation ofadhesive force which was conducted 100 times.

TABLE 5 Ratio of Defective Thickness Ratio of Adhesive Force of ofSilicone Occurrence Water-Repellent Film Resin of Ion (Ratio ofDefective Film (nm) Migration Mountability) Example 13 60 0/18 0/100Example 14 90 0/18 0/100 Example 15 100 0/18 1/100 Comparative 300 0/1815/100  Example 11 Comparative 500 0/18 60/100  Example 12 Comparative100 16/18  0/100 Example 13

As shown in Table 5, it was confirmed that, within a range of athickness of a silicone resin film not greater than about 100 nm, theoccurrence of ion migration was effectively reduced or prevented, theadhesive force of a water-repellent film was low, and excellentmountability was obtained. In the electronic components according toComparative Examples 11 and 12, the occurrence of ion migration was notobserved, however, the adhesive force of a water-repellent film was highand the mountability was not satisfactory. In the electronic componentaccording to Comparative Example 13, the mountability was satisfactory,however, the occurrence of ion migration was observed.

In each of the first to fourth preferred embodiments and Examples 1 to15 above, features can be combined with each other as appropriate.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. An electronic component, comprising: anelectronic component main body; first and second external electrodesprovided on a portion of a surface of the electronic component mainbody; and a water-repellent film provided on another portion of thesurface of the electronic component main body and on a surface of thefirst external electrode and containing a non-cross-linked siliconeresin; wherein the non-cross-linked silicone resin has a weight-averagemolecular weight not less than about 7400 g/mol and not more than about8000 g/mol.
 2. The electronic component according to claim 1, whereinthe electronic component main body includes first and second mainsurfaces extending along a length direction and a width direction, firstand second side surfaces extending along the length direction and athickness direction, and first and second end surfaces extending alongthe width direction and the thickness direction; on the second mainsurface, a tip end portion of the first external electrode and a tip endportion of the second external electrode are opposed to each other inthe length direction; and the water-repellent film is located on aportion of the second main surface, which is located between the tip endportion of the first external electrode and the tip end portion of thesecond external electrode.
 3. The electronic component according toclaim 1, wherein the water-repellent film extends across the anotherportion of the surface of the electronic component main body and thesurface of the first external electrode.
 4. The electronic componentaccording to claim 1, wherein the water-repellent film covers an entiresurface of an exposed portion of the electronic component main body andeach of the first and second external electrodes.
 5. The electroniccomponent according to claim 1, wherein each of the first and secondexternal electrodes includes a plurality of layers, and an outermostlayer of each of the first and second external electrodes contains atleast one of Sn, Cu, and Ag.
 6. A mount structure of an electroniccomponent, comprising: the electronic component according to claim 1; amount substrate on which the electronic component is mounted; and solderjoining the electronic component and the mount substrate to each other.